1. Field of the Invention
The present invention relates to an optical disc apparatus, and more particularly to a reduction of power consumption associated with driving of an optical disc and driving of an optical pickup.
2. Description of the Related Art
In order to reduce current consumed during operation, CD drives, DVD drives, or the like of portable type conventionally employ technology for controlling a motor (spindle motor) for rotating an optical disc and a motor (thread motor) for driving an optical pick-up in a radial direction of the optical disc to execute seeks so as to prevent concurrent driving of the two motors.
For example, in Japanese Patent Laid-Open Publication No. 2000-251272, technology where operation of a spindle motor for rotating an optical disc is disabled by activating current control means whenever seek control means moves an optical head is disclosed.
Because a spindle motor expends a relatively large current, by temporarily restricting rotative driving of the optical disc as described above, it becomes possible to suppress an increase of current consumption. On the other hand, because rotative driving of the optical disc is restricted, there arises a problem that the time lapse before the optical disc attains the target rotational speed becomes longer.
It is assumed that, for example, a drive goes into standby mode after a lapse of a predetermined time since the drive accepted the last access from a host device such as a notebook PC. In the standby mode (power-saving mode), the drive returns to normal operation mode (resumes) when a read command is issued by the host device. In this normal operation mode, if the rotative driving of the optical disc is temporarily paused during seek movement, the rotational speed of the optical disc would decrease due to a rotation load, thereby causing a longer time to elapse before attaining the target rotational speed of the optical disc. When the optical disc does not attain the target rotational speed, reproduction rate does not increase adequately. The lower reproduction rate produces a problem that originally included reproduction performance cannot be delivered.
FIG. 9 shows changes of the rotational speed and current consumption with respect to time in a prior-art drive. When the drive resumes from standby mode by a read command input from the host device, a spindle motor accelerates the optical disc to gradually increase the rotational speed of the disc. However, when rotative driving by the spindle motor is temporarily paused to execute seek movement, the rotational speed of the optical disc decreases due to rotation load. After desired data is read, the spindle motor is reactivated to accelerate the optical disc. Because the spindle motor is again paused to initiate seek movement when the read command is further input, the optical disc spends a longer time attaining the target rotational speed, thereby forcing data reading at low reproduction rate.